Stealth authoritarianism is the term legal scholar Ozan O. Varol used in "Stealth Authoritarianism," 100 Iowa Law Review 1673 (2015) for regimes that "cloak repressive practices under the mask of law" and "imbue them with the veneer of legitimacy," which makes anti-democratic practices harder to detect.
Varol's emphasis is on authoritarians who "perpetuate their power through the same legal mechanisms that exist in democratic regimes," and on "the emerging reliance on legal, particularly sub-constitutional, mechanisms to perpetuate political power" (Varol 2015). In other words, the tools are often ordinary statutes and procedures rather than constitutional ruptures.
Related concepts
The idea sits close to Kim Lane Scheppele's autocratic legalism and to Sergei Guriev and Daniel Treisman's spin dictators. On this site, Venezuela's 2004 Supreme Court law is presented as an example of the pattern.