There are restrictions on sending citrus seeds into citrus producing states like CA, FL, TX. For instance, there is this one from TX that specifically mentions seed (this covers intra-US shipments, not just from outside the US, interestingly it allows materials from CA and FL but not other states):
TITLE 4. AGRICULTURE
Part I. Texas Department of Agriculture
Chapter 5. Quarantines
Citrus Seed, Citrus Budwood, and Citrus Nursery Stock Quarantine
4 TAC sec.5.152, sec.5.153
The Texas Department of Agriculture proposes amendments to sec.5.152 and
sec.5.153, concerning restricted shipments of Citrus Seed, Citrus Budwood, and
Citrus Nursery Stock. The department proposes amendments sec.5.152 and sec.5.153
to include the State of California. Currently, citrus seeds, citrus budded
nursery stock or seedlings, citrus budwood, or any part of any citrus tree or
seedling may not be shipped, carried, or in any way transported by any means
into the State of Texas. Florida is the only state allowed to ship into this
state under certain conditions. It is necessary to amend the restricted shipment
section and the restrictions on citrus seed shipment section to include
California as a state from which citrus products may be imported because
California is a disease-free source of certified citrus budwood and citrus seed
for Texas producers.