[JURIST] Spain's conservative Popular Party [official website in Spanish] Friday filed a constitutional challenge against a law passed earlier this year which legalizes gay marriage [JURIST report] and allows homosexual couples to adopt children. The party filed the case in Spain's Constitutional Court [official website in Spanish], saying that the new law "denaturalizes the fundamental institution of marriage." Since it was passed, dozens of gay couples have married and several others, including high-ranking public officials, have applied for marriage licenses. Popular Party head Mariano Rajoy [BBC profile] said the party had presented a civil union alternative to marriage when the measure was passed. Spain is the third European nation to have legalized gay marriage, following Belgium and Holland. EFE has more.