ity ▁opinion ▁Under ▁the ▁F SI A , ▁a ▁foreign ▁government ▁is ▁pres um pt ively ▁imm une ▁from ▁suit ▁in ▁federal ▁court ▁unless ▁a ▁specific ▁exception ▁applies . ▁This ▁case ▁involves ▁the ▁exception ▁for ▁" right s ▁in ▁imm ov able ▁property ▁situated ▁in ▁the ▁United ▁States ." ▁The ▁question ▁before ▁the ▁Supreme ▁Court ▁was ▁whether ▁a ▁suit ▁declaring ▁the ▁valid ity ▁of ▁a ▁tax ▁li en ▁places ▁" right s ▁in ▁imm ov able ▁property " ▁in ▁issue . ▁ ▁A ▁" li en " ▁is ▁a ▁" charge ▁or ▁security ▁or ▁inc umb rance ▁upon ▁property ." ▁An ▁" inc umb rance ," ▁in ▁turn , ▁is ▁any ▁" right ▁to , ▁or ▁interest ▁in , ▁land ▁which ▁may ▁subs ist ▁in ▁another ▁to ▁the ▁dimin ution ▁of ▁its ▁value ." ▁A ▁tax ▁li en ▁" in hib its ▁one ▁of ▁the ▁qu int ess ential ▁rights ▁of ▁property ▁ownership — the ▁right ▁to ▁convey ▁that ▁property . ▁Thus , ▁a ▁suit ▁to ▁declare ▁the ▁valid ity ▁of ▁a ▁tax ▁li en ▁in question ably ▁places ▁" right s ▁in ▁imm ov able ▁property " ▁in ▁issue . ▁ ▁This ▁interpretation ▁is ▁consistent ▁with ▁the ▁prev ail ing ▁view ▁of ▁international ▁law ▁in ▁ 1 9 7 6 , ▁the ▁year ▁F SI A ▁was ▁en act ed . ▁Under ▁international ▁law , ▁so ver eign ▁imm unity ▁exists ▁for ▁inher ently ▁public ▁acts ▁but ▁not ▁with ▁respect ▁to ▁private ▁acts . ▁Property ▁ownership ▁was ▁held ▁to ▁not ▁be ▁an