Jamaica’s government on Thursday announced a major rethinking of its marijuana laws, including plans to partly decriminalize small amounts of marijuana and to allow possession for religious, scientific and medical purposes. Justice Minister Mark Golding said the cabinet was backing a proposal to make possession of no more than two ounces of marijuana a petty offense that would result in a fine but not an arrest. The proposed changes “are not intended to promote or give a stamp of approval” to the use of the drug for recreational purposes, Mr. Golding said, but to provide “a more enlightened approach to dealing with possession of small quantities.” The current law prohibiting marijuana remains in effect for now, but lawmakers are likely to amend it.