The question is only of perfect fulfilment
Thesis XXXV. This makes it plain that the doctors of the Reformed Church do not deny that believers, by Christ's grace, can in some way and in some sense fulfil the law and keep God's commandments, that is, by giving them true obedience.
So when they sometimes say that it is impossible even for believers to fulfil God's law and observe its commandments, their meaning is not any fulfilment or observance at all, but only one that is perfect and absolute. They take care to point this out when they set out the state of the question.
At that point they all note, with Chemnitz in his Examen of the sixth session of the Council of Trent, that the question between the papists and the Protestants is not simply whether the law can be fulfilled by God's grace, but whether it can be fulfilled perfectly. For the Protestants readily grant the regenerate a begun and imperfect fulfilment of it.
Latin
XXXV. Ex his manifestum est Ecclesiae Reformatae Doctores non negare fideles per Christi gratiam aliquo modo, & sensu posse legem implere, & Dei mandata servare, veram, scilicet, iis praestando obedientiam. Itaque quum aliquando dicunt fidelibus ipsis impossibile esse implere Dei legem, & observare illius mandata, id juxta eorum mentem, exponendum est non de quavis impletione & observatione, sed de illa demum quae sit perfecta atque absoluta: quod diligenter monent, quum quaestionis hujus statum explicant. Tum enim observant omnes, cum Chemnitio, in Examine Sessionis sextae Concilii Tridentini, inter Pontificios & Protestantes non quaeri simpliciter, An lex per Dei gratiam impleri possit, sed an possit impleri perfecte. Cum inchoatam atque imperfectam ejus impletionem Renatis ultro concedant Protestantes.