Acquiescence prevents relief when a plaintiff knowingly permits infringement and the defendant materially changes position to its prejudice. Acquiescence is an equitable defence where the claimant's words or conduct amount to assent or forbearance that allows another to infringe rights and expend resources, creating an inference of consent or licence. It requires specific knowledge or clear conduct inconsistent with asserted exclusive rights, and will bar relief when the defendant has relied and changed position to its prejudice so that granting the remedy would be unjust; mere delay or silence without such conduct is insufficient.