Don H. Dwyer Jr., a Republican member of the House of Delegates, plans to bring impeachment charges on the House floor on Wednesday against the state’s attorney general, Douglas F. Gansler. Mr. Dwyer said that Mr. Gansler overstepped his authority in issuing a legal opinion last month saying the state would recognize same-sex marriages from other places and ordering state agencies to give gay married couples the same rights as heterosexual couples. Mr. Gansler’s opinion does not change the law, but it was meant to guide state officials. The impeachment matter is most likely to be dismissed by the House speaker, Michael E. Busch, a Democrat. If so, Mr. Dwyer has said he will probably call for a ruling from the full House, which is controlled by Democrats.