But they knew what to loot

In Communist East Germany 'the people' knew about art; it was there for the taking;

The pattern was always the same: Tax inspectors together with Stasi officers would arrive at the break of dawn and accuse private collectors of running a commercial operation. Tax evasion charges would follow, along with an unreasonably high tax bill.

By the 1970s, GDR authorities had perfected a system of acquiring works of art that was as cynical as it was savage. [Collector Heinz] Dietel's case was just one of an estimated 150 to 200 that occurred during the 1970s and 80s after fewer and fewer members of the public were willing to sell works to the state authorities and the economic situation worsened.

The vast majority of pieces were sold to dealers in the West where there was no shortage of buyers willing to turn a blind eye to the provenance of submarket-value artworks.

But a lot of it still remains in museums in the former East Germany, and for the rightful owners, their time is nearly up;

It wasn't until the reunification of Germany years later that prospects brightened. In 1994, a Compensation Act was introduced, entitling the original owners of certain forms of confiscated property, including artworks, to compensation.

But there was a caveat: Since a significant proportion of confiscated artworks and other objects were housed in national museums in the former East Germany, the Compensation Act contained a separate clause to prevent the sudden stripping of those collections. The clause stated that those institutions had 20 years to reach a settlement with the owners in question and would retain the right to exhibit the works free of charge during that time.

With that legal caveat due to expire in 2014, museums will be forced to return works to their original owners should they fail to reach a deal.