Long-repressed contradictions have a way of flaring up in public in times of stress. China is suddenly at the center of two of them, and they could well entail significant global diplomatic and economic consequences.

In the first case, Beijing’s signal on Thursday that it intends to tighten legislative restrictions on Hong Kong under the rubric of national security has brought to the surface the inherent inconsistency of the “one country, two systems” paradigm that has governed the relationship between the two for almost three decades. Underpinned by the 1997 agreement that governed the U.K.’s hand-off of Hong Kong to China, it promised a 50-year transition for many elements of Hong Kong’s economic, financial, institutional and political structure.

With time, this notion of “one country, two systems” has come under increasing pressure, fueling a tug-of-war between China and the pro-democracy movement in Hong Kong that has periodically erupted in street protests. It has also increased tensions between China and other countries. Both would intensify if Thursday’s announcement were to be codified in legislation.