"World Maker… With this proof, the queen will have enough justification to completely outlaw this guild within Hydrurond's territory," Arthur said.
During wartime, all the guilds from the opposite country were automatically outlawed. This was to prevent the members of the guilds from sabotaging the country from the inside. Hence, Deekoff and his other friends shouldn't be able to roam Hydrurond's cities. That's why they needed places such as this shop to hide.
But this restriction was only temporary. After the war, the guilds would be allowed access again. Just like how members of Everlasting Heavenly Legends were still able to roam in Verremor after Verremor invaded Themisphere.