Spain has a law since Dec2011 concerning invasive plants. It is now against the law to possess, sell, import and export following plants:
IN ALL SPAIN (if not indicated otherwise):
Acacia dealbata (permitted in Canary and Balearic Islands, prohibited in the peninsula)
Agave americana
Ailanthus altissima (permitted in Canary Islands)
Alternanthera philoxeroides
Ambrosia artemisiifolia
Araujia sericifera
Asparagus asparagoides
Azolla spp.
Baccharis halimifolia L.
Buddleja davidii
Cabomba caroliniana
Carpobrotus acinaciformis, C. edulis (permitted in Canary Islands)
Cortaderia spp. (permitted in Canary Islands)
Cylindropuntia tunicata
Egeria densa
Eichhornia crassipes
Elodea canadensis (permitted in Canary Islands)
Fallopia japonica / Reynoutria japonica
Helianthus tuberosus
Heracleum mantegazzianum
Ludwigia spp.(except L.palustris)
Myriophyllum aquaticum
Opuntia dillenii, O. maxima, Opuntia stricta
Pennisetum setaceum
Pistia stratiotes
Salvinia spp.
Senecio inaequidens
Spartina alterniflora, S. densiflora, Spartina patens
Tradescantia fluminensis
Prohibited in BALEARIC ISLANDS:
Cotula coronopifolia
Pennisetum villosum
Pennisetum clandestinum
Prohibited in CANARY ISLANDS:
Acacia farnesiana and A. salicina
Ageratina adenophora and A. riparia
Arundo donax
Atriplex semilunaris
Calotropis procera
Cyrtomium falcatum
Furcraea foetida
Ipomoea indica
Leucaena leucocephala
Maireana brevifolia
Nassella neesiana
Pennisetum clandestinum
Pennisetum purpureum
Phoenix dactylifera
Ulex europaeus
It is noted, that 3/4 of the invasive plants in Spain originate from gardening and floristic practices.