On June 20, 1815, Lewis Cass, governor of Michigan territory, wrote to acting Secretary of War Dallas, that the possession of the former privileges of trade which the British had enjoyed among the Indians of the northwest was a subject which the government should take up for consideration.
Just a few months later, October 18, special commissioners, William Clark, Ninian Edwards, and August Chouteau...reported that British traders were constantly intriguing among these tribes... .
These official reports had their effect upon the government. [Source]
From another blog post, One Of Many Missions….., about the military and also Lewis Cass's contributions in Michigan:
The Territorial Government determined that their new acquisitions on the Saginaw would be utterly worthless unless the articles of the Treaty of Saginaw could be carried out in full.