Melchior Wathelet, a Belgian advocate general in the European Court of Justice, said gay spouses have equal rights in countries even where governments were implacably opposed to same-sex marriage.
Although opinions by advocates are non-binding, they are often followed by the full court when a decision is made in the coming months.
The opinion was given on the case of a Romanian national, Adrian Coman, who wishes to build a life in Romania with his American husband, Claibourn Robert Hamilton, who he lived with in the US before marrying in Brussels in 2010. Romania is one of six countries in the EU where it is not yet legal for same-sex partners to marry.
The EU’s freedom of movement principle grants rights to an EU citizen’s spouse, without specifying how spouse is defined.