。
Love can't be held back by reason.
Literal
Romantic-love [topic-は] reason [instrumental-では] cannot-be-suppressed.
A clean aphorism. では here is the contrastive form of で (instrumental 'by means of') — 'by reason at least, it can't be done.' The verb 抑える ('to suppress, hold down') becomes the passive 抑えられる, used here in its potential sense ('cannot be suppressed') — a single form that covers both passive and potential, ambiguity Japanese tolerates because context disambiguates.