OYAT > Paris, France > Firm Profile

164 rue du
Faubourg Saint-Honoré
75008 Paris

France > Administrative and public law Tier 3

OYAT is retained by leading companies and public entities, including cities, regions and universities. The firm houses strong public procurement expertise, advising on significant matters in the rail, construction and IT sectors, while its team also regularly handles strategic contentious and non-contentious real estate and construction work. The group is also consulted on regulatory issues, notably in the TMT sector. Practice head Laurent de la Brosse has extensive experience and Romain Canot also contributes.

Practice head(s):

Laurent de la Brosse

Other key lawyers:


‘Availability, responsiveness, tight team. OYAT always provides measured, precise and well-argued opinions and analyses.’

‘Laurent de la Brosse stands out for his perspective and objectivity on each file. He has very specific expertise in public business law. He never has any preconceptions or certainties on the subjects submitted to him. Laurent de la Brosse demonstrates great perspective and great objectivity of analysis.’

‘Very present and responsive team. Clear and operational answers.’

‘Laurent de la Brosse knows our requirements particularly well’

‘The team is attentive and available. Offers suitable solutions.’

‘Multidisciplinary team, available and flexible.’

‘Responsive and competent team.’

Key clients

Bordeaux Métropole

Haropa – Port de Paris

Office des Transports de Corse

Région Hauts de France

Région Nouvelle Aquitaine

Région Bourgogne Franche Comté



Campus Agro

Département des Hauts de Seine


Région Grand Est

Région Bretagne

Voies Navigables de France

Epaurif (Etat)

Université Paris Saclay

SPL Grand Est Mobilités

Région Normandie

Région PACA

Département des Pyrénées Orientales

Work highlights

  • Advising the French State in the context of the implementation of the concession contract for the transformation of the former Val de Grace Hospital (Paris 6) into a digital health campus (400 million EUR of investment).
  • Advising Demathieu et Bard on the procedure for awarding the partnership contract for the construction of the Centre Pompidou Francilien – “Fabrique de l’art – pôle de conservation et de creation.”
  • Advising Canal France International on all issues related to the law of public procurement in consulting and litigation (drafting of legal opinions, review of consultation files).

France > Industry focus: IT and internet  Tier 3

Acting for domestic and international clients alike, OYAT serves the digital and IT needs of major public and private bodies. The established team is well positioned to advise on outsourcing, digital transformation and licensing issues, as well as handling litigation. New technologies, such as AI and robotics, are another area of expertise for the group. Industry veteran Marie-Hélène Tonnellier leads the team, and is noted for her in-depth knowledge of IT, media, e-commerce and data protection issues. Charlotte Barraco-David is likewise recommended.

Practice head(s):

Marie-Hélène Tonnellier

Other key lawyers:


‘Although the team is small, it is comprehensive in its coverage of the technology sector. The team is experienced and is very much at the forefront of developments in the technology sector.’

‘They are always responsive and provide very clear and practical advice. We have full confidence in them and their abilities, particularly to deal with English-speaking clients. They are also very reasonable in terms of fees.’

‘Marie-Hélène Tonnellier is a well-known name in the technology sector and is always seen at the key technology law conferences, both as participant and speaker. She has incredible breadth of expertise and is always super responsive. She works very hard for clients and is passionate about getting the best outcomes for them. As well as her incredible technical abilities she is also extremely charming and wonderful to work with. I would highly recommend her to my clients and have done so on many occasions over the years.’

‘Highly responsive and display an excellent sense of understanding client needs. They are very easy to deal with and this is achieved by establishing an excellent relationship of trust and confidence. Their fees are reasonable and they provide commercial and pragmatic solutions that are clearly explained and expertly documented.’

‘Marie-Hélène Tonnellier and her team have a wide range of skills and experience that cover the broad range of TMT issues and the standards of excellence are high whatever the issue. I am therefore able to refer work to them with absolute confidence in their knowledge of their sector particularly with regard to artificial intelligence, data exchange and new developments such as the Data Act and the Data Governance Act, which are raising important new challenges for our clients.’

Key clients

Hachette Livre


Sopra Steria



Edreams Odigeo


Pôle emploi


ESA (European Space Agency


Service d’Information du Gouvernement (SIG)

Work highlights

  • Advising Edreams Odigeo, a major online travel company, on various IT issues.
  • Advising the Service d’Information du Gouvernement on all its digital issues, and particularly on the setting up of a platform called the State Design System.
  • Assisting Nouvelle Aquitaine Mobilité with the drafting and negotiation of all contracts with selected IT service providers.

France > Private equity: venture/growth capital Tier 3

Practice head(s):

Caroline Basdevant-Soulié; Guillaume Ledoux


‘A high-quality team. Caroline Basdevant-Soulié: exceptional, deal maker, attentive, good technical skills.’

‘The Oyat team is very dynamic, pragmatic with a very pleasant and friendly relationship while being professional.’

‘Caroline Basdevant-Soulié for her pragmatism, flexibility and quick and efficient responses.’

‘The team is very professional, available and attentive to the expectations of its customers. It facilitates negotiations and the progress of projects.’

‘Caroline Basdevant-Soulié has extensive expertise in private equity operations. She perfectly understands the business challenges of her clients.’

‘Caroline Basdevant-Soulié and Guillaume Ledoux: very competent, very good interpersonal contact, efficient.’

Key clients

Arpilabe Holding

Arcadis ESG


Daikin Air Conditioning France

Icade (Urban Odyssey)

Yotta Capital





Van De Velde Packaging Group

Accor / Dedge

Work highlights

  • Advised Sébastien Kher (CEO of Nomios Group) and the Nomios’ managers regarding the local and international coordination of the sale of international Nomios Group by Keensight Capital.
  • Advised Urban Odyssey, a subsidiary of Icade, on their investments in 5 start ups.

Oyat is a law firm with a pioneering spirit, a pool of talent bringing together professionals recognized for their excellence in M& A, private equity, public law, environmental law, energy law, digital and IP, commercial law, real estate and litigation.

Everyone works with agility, in France and abroad, relying on an extensive network of experts located mainly in Europe, Asia and the United States to provide each client with the strategic and operational support required.

Like the oyat, the agile and robust “binder plant” that ensures the cohesion, unity and durability of the dune in the face of the elements, this collective intelligence is a real strength. Combined with an entrepreneurial spirit, it allows the firm to project itself into the challenges of tomorrow with a vision of committed lawyers, constantly attentive to economic, societal and technological changes. At Oyat, each client has the opportunity to build a dedicated team of multi-specialists by combining the expertise, synergies and flexibility necessary to address its complex issues. Its lawyers, experienced in teamwork in project mode, practice their profession for, but also and above all, alongside their clients. Conceiving their role as a partner and strategy advisor, they are capable,through their experience, of intervening both in anticipating their clients’ problems and in helping them define the best strategy on innovative or defensive issues requiring listening, understanding,tenacity, rigor and competitive spirit.

Attentive to a changing world, its partners seek to guide and accompany each Oyat lawyer in a spirit of ambition and surpassing oneself, but also of solidarity and listening.

Department Name Email Telephone
Paris Basdevant-Soulié Caroline c.basdevant-soulie@oyat.law 00 33 1 81 22 40 11
Paris Tonnellier Marie-Hélène mh.tonnellier@oyat.law 00 33 1 81 22 40 10
Paris De la Brosse Laurent l.delabrosse@oyat.law 00 33 1 81 22 40 12
Photo Name Position Profile
Caroline Basdevant-Soulié photo Caroline Basdevant-Soulié Partner
Caroline Basdevant-Soulié photo Caroline Basdevant-Soulié Partner
Romain Canot photo Romain Canot Partner
Guillaume Ledoux photo Guillaume Ledoux Partner
Marie-Hélène Tonnellier photo Marie-Hélène Tonnellier Marie-Hélène Tonnellier is the head of the Digital/IP department and advises on…
Laurent de la Brosse photo Laurent de la Brosse Member of the Paris Bar since 1999, Laurent de La Brosse co-founded…