Preemption

The act or right of purchasing before others.

The privilege or prerogative formerly enjoyed by the king of buying provisions for his household in preference to others.

The right of an actual settler upon public lands (particularly those of the United States) to purchase a certain portion at a fixed price in preference to all other applicants.

the right to purchase something in advance of others

the right of a government to seize or appropriate something (as property)

the judicial principle asserting the supremacy of federal over state legislation on the same subject