Very important case to consider:
http://supreme.justia.com/us/339/707/case.html
After reading that you might notice 2 important references in there.
The resolves of 1845 to cede republic of texas and another reference was
Compromise of 1850 where a ratification had taken place of exactly what
parts of it were ceded. Republic of Texas sold off some of it's land due
to high debt that needed settled. The rest was later transferred to
federal government probably because of that same debt problem
from fighting off mexico.
So it was not done at the nations capital , it was done at the capital
for the republic of texas right underneath everyone's noses.
Although still yet people have their opinions of what really happened at the Alamo.