Why was Jefferson's decision to purchase the Louisiana Territory considered by some to be hypocritical?

Thomas Jefferson certainly acted in a way that was contrary to his political beliefs when he agreed to purchase the Louisiana Territory from France.  However, this does not necessarily mean that he was a hypocrite.  It is not necessarily the case that political leaders should stick fanatically to their principles even when it would be better for the country if they were to bend a little. Jefferson believed in a strict construction of the Constitution.

to regulate production on things such as fuel and production