The precedent set by a Supreme Court decision regarding censorship or any other issue does not become "permanent" in the legal sense; rather, it establishes a legal principle that is expected to be followed unless and until it is overturned or modified by future Supreme Court decisions. Here's how this works:

1. **Precedent Setting**: When the Supreme Court makes a decision, it sets a precedent, often referred to in legal terms as "stare decisis" (to stand by things decided). This means that lower courts in the U.S. are generally bound to follow this decision in similar cases.

2. **Reversal by Future Courts**: However, the Supreme Court itself is not strictly bound by its own precedents. A future Supreme Court, potentially with different justices or under different circumstances, can revisit the issue. If there's a compelling reason, such as a change in societal values, new technology, or a shift in legal interpretations, the court might choose to overturn or modify the previous ruling. 

3. **Examples of Overturned Precedents**: There are historical examples where the Supreme Court has overturned its own past decisions. For instance, the landmark case of *Brown v. Board of Education* (1954) overturned *Plessy v. Ferguson* (1896), moving from "separate but equal" to integration in public schools.

4. **Political and Judicial Dynamics**: The composition of the Supreme Court can change over time due to new appointments by different presidents. If the court's ideological balance shifts, this might lead to revisiting and possibly overturning previous decisions. 

5. **Legislative Action**: Congress can also influence outcomes by passing new laws that might address or circumvent the court's decisions, although these can be challenged in court again.

6. **Public Opinion and Social Change**: Public opinion and societal changes can pressure the court to reconsider its stance on issues like censorship, especially with the advent of new technologies or social movements.

In the scenario you described, if liberal Supreme Court justices made a decision allowing a form of censorship, this could be:

- **Reversed** by a future Supreme Court with a different ideological makeup.
- **Modified** by subsequent decisions that might narrow or expand the scope of the original ruling.
- **Circumvented** by new laws or policies that aim to address the same issue differently.

Therefore, while the precedent would be influential and would guide legal interpretations until changed, it could indeed be reversed or significantly altered by future judicial, legislative, or societal developments.