The MAR Regulation provides a list of legitimate behavior (Article 9) and accepted market practices (Article 13) that apply in administrative prosecution. These defenses do not apply to all criminal offenses.  See Insider Dealing – France – Offenses 1.3.7,  1.3.8,  1.3.9,  1.3.10, and 1.3.11.

The criteria taken into account by a competent authority to establish an accepted market practice include:

• whether the market practice provides for a substantial level of transparency to the market;
• whether the market practice ensures a high degree of safeguards to the operation of market forces and the proper interplay of the forces of supply and demand;
• whether the market practice has a positive impact on market liquidity and efficiency;
• whether the market practice takes into account the trading mechanism of the relevant market and enables market participants to react properly and in a timely manner to the new market situation created by that practice;
• whether the market practice does not directly or indirectly create risks for the integrity of related markets, whether regulated or not, in the relevant financial instrument within the European Union;
• the outcome of any investigation of the relevant market practice by any competent authority or by another authority, in particular whether the relevant market practice infringed rules or regulations designed to prevent market abuse, or codes of conduct, irrespective of whether it concerns the relevant market or directly or indirectly related markets within the Union; and
• the structural characteristics of the relevant market, inter alia, whether it is regulated or not, the types of financial instruments traded and the type of market participants, including the extent of retail-investor participation in the relevant market.