can be reformulated with an extended participle

This is neither the Partizip I or Partizip II but the so called Gerundivum, or participium necessitatis. It's the third participle German has, and it's always built from the Partizip I. Never from the Partizip II.

So the answer is simple:

… eine Maßnahme, die nicht zu gestatten ist. ← zu-Infinitiv

may be rephrased as

… eine nicht zu gestattende Maßnahme. ← Gerundivum

Just as vor book says. This isn't a matter of active or passive because the Gerundivum is always built from the Partizip I.

can be reformulated with an extended participle

This is neither the Partizip I or Partizip II but the so called Gerundivum, or participium necessitatis. It's the third participle German has, and it's always built from the Partizip I. Never from the Partizip II.

So the answer is simple:

… eine Maßnahme, die nicht zu gestatten ist. ← zu-Infinitiv

may be rephrased as

… eine nicht zu gestattende Maßnahme. ← Gerundivum

Just as your book says. This isn't a matter of active or passive because the Gerundivum is always built from the Partizip I.