Complex sentence: He was concurrently elected in the 1867 Canadian election to the new Canadian House of Commons and Quebec Legislative Assembly and, under the law of the day, was allowed to sit in both legislatures at the same time.
Split into simpler sentences: He was concurrently elected in the 1867 federal election to the new Canadian House of Commons and to the Quebec Legislative Assembly. Under the law of the day, he was allowed to be a member of both legislatures at the same time.