Catalyzes the demethylation of isoprenylcysteine methylesters (By similarity). May act as a negative regulator of ABA signaling (PubMed:20868530). [protein]-C-terminal S-[(2E,6E)-farnesyl]-L-cysteine methyl ester + H2O = [protein]-C-terminal S-[(2E,6E)-farnesyl]-L-cysteine + H(+) + methanol Expressed at low levels in flowers and siliques. Increased sensitivity to abscissic acid (ABA) but slightly decreased sensitivity to salt and osmotic stresses during seed germination. Plants silencing ICMEL2 show enhanced ABA inhibition of seed germination. Belongs to the AB hydrolase superfamily. Isoprenylcysteine methylesterase family. Extended C-terminus.