I have noticed that Germany has two different for "checks within the territory" and when an (internal Schengen) border is crossed.
For crossing an (internal Schengen) border Germany is enforcing e.g. Article 13 Border crossing (in general Articles suitable only for external Schengen border).
In my opinion, such practice violates TITTLE III, CHAPTER I of EU 2016/399 "Absence of border control at internal borders" and Article 23 of EU 2016/399 "Checks within the territory"
Article 23 of EU 2016/399 Checks within the territory:
The absence of border control at internal borders shall not affect:
(a) the exercise of police powers by the competent authorities of the Member States under national law, insofar as the exercise of those powers does not have an effect equivalent to border checks; that shall also apply in border areas. Within the meaning of the first sentence, the exercise of police powers may not, in particular, be considered equivalent to the exercise of border checks when the police measures:
(i) do not have border control as an objective;
(ii) are based on general police information and experience regarding possible threats to public security and aim, in particular, to combat cross-border crime;
(iii) are devised and executed in a manner clearly distinct from systematic checks on persons at the external borders;
(iv) are carried out on the basis of spot-checks;
(b) security checks on persons carried out at ports and airports by the competent authorities under the law of each Member State, by port or airport officials or carriers, provided that such checks are also carried out on persons travelling within a Member State;
(c) the possibility for a Member State to provide by law for an obligation to hold or carry papers and documents;
(d) the possibility for a Member State to provide by law for an obligation on third-country nationals to report their presence on its territory pursuant to the provisions of Article 22 of the Convention implementing the Schengen Agreement of 14 June 1985 between the Governments of the States of the Benelux Economic Union, the Federal Republic of Germany and the French Republic on the gradual abolition of checks at their common borders (‘the Schengen Convention’).
Now, how to define a border control? For me a border control is a control at borders or border area which differs (typically is more strict) from a control within the territory (imagine a police control in a capital city far away from a border).
Therefore, if there are different standards for a control in border area and within the territory of Germany, in my opinion, this is illegal.
Some would definitely argue that based on Article 23(c) of EU 2016/399 a Schengen state have "the possibility for a Member State to provide by law for an obligation to hold or carry papers and documents" Again, I argue that based on Article 23 of EU 2016/399 "checks within the territory" have to be the same both in a border area and e.g. in a capital city.
I futher examined Article 23(c) of EU 2016/399:
Article 42 of EU 2016/399 Notification of information by the Member States
The Member States shall notify the Commission of national provisions relating to Article 23(c) and (d), the penalties as referred to in Article 5(3) and the bilateral agreements authorised by this Regulation. Subsequent changes to those provisions shall be notified within five working days.
The notifications are here (most of countries submitted it 24.1.2008 and then forgot about it, e.g. the Czech republic updated the Czech immigration law but it is not reflected in this notification):
Based on analysis of this notification is clear that some countries understand that border controls have been abolished on internal Schengen border by EU 2016/399 (EU 2006/562) and there are only "checks within the teritorry" even in border areas but some countries still setup rules "when a border is crossed" which is, in my opinion, a violation of TITTLE III, CHAPTER I of EU 2016/399 "Absence of border control at internal borders"
Please just compare in the notification Luxembourg and Germany where the difference is clear. In my opinion Germany shall enforce only Article 48 of AufenthG which corresponds to Article 23(c) of EU 2016/399.
Considering Schengen Borders Code EU Regulation 2016/399, is it legal to have 2 different standards for "checks within the territory" and when an (internal Schengen) border is crossed in Schengen area?