What were some complaints about the Louisiana purchase

The general opinion of many Americans at the time of the purchase was that Jefferson was being hypocritical by going through with it. Jefferson was known to have a strict interpretation of the Constitution and believed the president only had the powers the Constitution gave him. Since there was no Constitutional precedent for buying land to add territory to the United States, there was theoretically no Constitutional authority for the president to buy the land.

Many of those in the Federalist party (the opposing party to Jefferson's Democratic-Republicans) believed that he would have objected on Constitutional grounds if any of them had tried to do the same thing. Therefore, the Federalists were very much opposed to the purchase. They also believed that by buying land from France, they would alienate Great Britain, whom they wanted as a close ally.

The issue of slavery in the western lands of the Louisiana Purchase became a major issue in later years and part of the cause of the American Civil War.