Does it have a defense?

you don't

Host defenses that protect against infection include natural barriers (eg, skin and mucous membranes), nonspecific immune responses (eg, phagocytic cells [neutrophils, macrophages] and their...

a defense is a line-up of the defensive players that is played against the opposing offensive team

it blocks people that is trying to getthe ball

Only if it can be proven in a court of law that the actions were deemed reasonably justified in keeping yourself from harm...key word being "reasonably". Just don't abuse your right to do this (no...